1. Field of the Invention
The present invention relates to a microscope for inspecting a semiconductor wafer.
2. Description of Related Art
As a semiconductor device is highly-integrated, layers formed on a semiconductor wafer become diverse, and remaining layers on an edge portion and a portion having a predetermined thickness (hereinafter, referred to as bevel portion) of the semiconductor wafer become more difficult to remove. Such remaining layers on the edge portion and the bevel portion of the semiconductor wafer are transited to a chip portion of the semiconductor wafer during a dry-etching process and a wet-etching process and serve as particles that cause various defects of the semiconductor wafer.
FIG. 1 is a plan view illustrating a typical semiconductor wafer, and FIG. 2 is a cross-sectional view taken along line II—II of FIG. 1. The semiconductor wafer undergoes several processes such as a process for depositing a layer on a surface thereof, a process of patterning the deposited layer, and a process of ion-implanting an impurity. However, these processes are not performed only on a surface of the wafer W. In other words, a layer can be deposited on an edge portion E, a bevel portion B and even a bottom portion L of the semiconductor wafer. The remaining layer on the edge portion E, the bevel portion B and the bottom portion L serves as a source of particles that affects a chip portion C of the semiconductor wafer W and causes various defects such as a contamination of the semiconductor wafer, thereby lowering a manufacturing yield.
In order to overcome the problem, a process of whittling the bevel portion B using an oxide wet-etching technique is added to suppress the defect of the semiconductor wafer. However, this has a problem in that a process is complicated and cannot solve a fundamental level of defects resulting from the edge portion and the bevel portion of the semiconductor wafer.
FIG. 3 shows a process of inspecting a semiconductor wafer using a conventional microscope. In order to inspect defects on the semiconductor wafer, first the semiconductor wafer W having defects resulting from the edge portion E and the bevel portion B thereof is conveyed to an analysis room.
The defective semiconductor wafer W is laid on a sample piece stage 1, and then defective portions and an edge portion E are inspected using a microscope 5. The sample piece stage 1 is configured to perform only a horizontal shift and a vertical shift, i.e., x-axis direction (left and right), y-axis (upper and lower) and z-axis movements (up and down). However, the sample piece stage 1 doesn't have a horizontal rotation function or a vertical rotation function.
Therefore, in order to inspect the bevel portion B of the semiconductor wafer W, a piece of the semiconductor wafer W to be inspected is manually cut using a diamond knife 2. The cut piece of the semiconductor wafer W is attached on a wafer holding jig 3 having a predetermined tilt angle using a carbon tape. In other words, in order to inspect the bevel portion B of the semiconductor wafer W, several wafer holding jigs 3 each having a different tilt angle are required.
FIG. 4 is a photograph illustrating the edge portion of the semiconductor wafer, and FIG. 5 is a photograph illustrating the bevel portion of the semiconductor wafer. As shown in FIGS. 4 and 5, defects are found in the edge portion and the bevel portion of the semiconductor wafer W. Such defects are transited to the chip portion C of the semiconductor wafer W and serve as contamination elements that contaminate the chip portion C of the semiconductor wafer W.
The conventional microscope described above has the following disadvantages. First, since the sample piece stage just performs a horizontal shift and a vertical shift, it is impossible to simultaneously inspect the edge portion and the bevel portion of the semiconductor wafer, thereby increasing the wafer inspection time. Second, during handling of a wafer sample piece, such as conveying and cutting a defective semiconductor wafer, other contamination of the wafer sample piece can occur, whereupon the inspection data can have errors. Third, since regular monitoring is not performed during a process of manufacturing the semiconductor wafer, it is difficult to find and prevent defects in advance. Fourth, in order to inspect different tilts of the bevel portion of the semiconductor wafer, many wafer holding jigs each having a different tilt angle are required. Finally, it is difficult to precisely inspect the semiconductor wafer having defects in the edge portion and the bevel portion and to clearly analyze or clarify defect factors, and also the inspection time is long, such that an appropriate remedy cannot be performed.